1. Field of the Invention
This invention relates to a method of estimating a cumulative exposure to a component of a gas and apparatus therefor.
2. Description of the Related Art
It is frequently desirable to obtain an estimate of a cumulative exposure of people or things to a component of a body of gas to which they are exposed. For example this may be important where a component is potentially toxic and where a body of gas is to be breathed by human beings. It may also be desirable to establish such exposure of objects to a component of a body of gas in an enclosed space for example the level of oxygen in an inert atmosphere, or an insecticide in a greenhouse atmosphere.
Such estimates are commonly performed using apparatus which draws the gas through an absorbent using a pump. However pumps may be relatively expensive and if they do not pump at the intended rate due for example to an electrical fault or battery discharge or other fault, it can lead to a wrong estimate of the cumulative exposure. They may also be inconvenient for a worker to wear if the worker's personal exposure to the component is to be estimated during a period of work.